That describes his role in Seattle's defense the past two years and how the team sees him in relation to the future of its roster.

Whether Chancellor remains part of that nucleus is a question that reflects one of the challenges an NFL team faces in the salary-cap era: Collecting the talent for a championship-caliber roster is only part of the equation. Retaining it is another.

That challenge lurked in the background a week ago, even as Seattle made waves by trading for receiver Percy Harvin and signing defensive ends Cliff Avril and Michael Bennett. Would Seattle's shopping spree end up costing Seattle one of its young defenders?

The Seahawks don't think so. In fact, their moves were predicated on the team's belief it could still retain its core. That brings us to Chancellor, who has one year remaining on the four-year contract he received as a rookie. He's eligible for a contract extension, and whether Seattle can sign him will be the first test of the market forces that will be tugging at the fabric of this emerging contender.

Success comes at a cost in today's NFL. Not only do players want to be rewarded for their role on winning teams, but they become more valuable in the eyes of other teams seeking to poach parts off a contender.

The Seahawks want to retain Chancellor, which is the first step. Whether they will be able to do so gets into that gray area that involves salary-cap space, open-market value and asking price. This is a question that won't necessarily be answered in the next couple weeks or even the next couple of months. Seahawks coach Pete Carroll and general manager John Schneider haven't spoken in anything but general terms about their plans for retaining young players, while Chancellor's agent did not return multiple messages.

Chancellor is emblematic of the way Seattle has built this defense with players who were overlooked and oversized, and wouldn't fit in every defensive system. Chancellor also epitomizes the challenge that Seattle will face in retaining the key parts of this defense that allowed the fewest points in the league last season.

He is 6 feet 3, 242 pounds, big enough to have some speculate he should play linebacker. But he was athletic enough to play quarterback in high school.

Seattle chose Chancellor in the fifth round in 2010, John Schneider's first draft as Seahawks general manager. Chancellor is strictly a strong safety. He's big enough to be the eighth man in the box against the run and a sledgehammer looming when opponents throw over the middle. He made the Pro Bowl as an injury alternate in his second season.

The bill is coming due for that success, and this is a decidedly different phase in team-building, one the Seahawks have not really had to consider in the past three years when they were rebuilding, a process that's as much about subtraction as it is addition.

Out with the old, and in with the new. Seattle didn't re-sign free agents like Nate Burleson and Cory Redding in 2010. It cut T.J. Houshmandzadeh and Julius Jones in 2010 and linebacker Lofa Tatupu the following year. Walter Jones retired in 2010 and Matt Hasselbeck was not re-signed in 2011. Re-signing veterans like defensive linemen Brandon Mebane and Red Bryant was the exception.

And now the question isn't so much who Seattle wants to keep, but how many players it can afford to retain. That concern tempered expectations entering free agency two weeks ago because Seattle must plan now for the reality that players like Richard Sherman, Earl Thomas — and perhaps most important, Russell Wilson — will be in line for top-shelf contracts over the next few years.

But Chancellor's contract is up first. He turns 25 next month and has just one year remaining on his deal. He'll be the first test of the team's ability to retain its talented core.